1. Field
The present invention relates to image recording apparatuses, image recording methods, and storage media.
2. Description of Related Art
Image recording apparatuses that record an image by repeating a recording scan and a sub-scan are known. In the recording scan, ink is ejected while a recording head having a plurality of recording nozzles for ejecting ink arrayed therein is moved in a scanning direction relative to a unit area of a recording medium. In the sub-scan, the recording medium is conveyed in a conveying direction that intersects with the scanning direction. In such image recording apparatuses, a so-called multipass recording method is employed, through which an image is formed by carrying out the recording scan a plurality of times on a unit area on the basis of divided image data formed by mask patterns in which recording permitted pixels, for which recording is permitted to be carried out through respective scans, are disposed.
In addition, in recent years, print materials of a variety of uses have been produced through ink jet recording, and various types of inks and recording media have been used accordingly. Japanese Patent Laid-Open No. 1-113249 discloses a method in which, with the use of ink containing a resin emulsion and a recording medium having poor water absorbency, the ink is heated when the ink lands on the recording medium so as to cause the resin emulsion to form a film and coloring materials contained in the ink is fixed to the recording medium.
However, if an image is recorded with the use of the ink and the recording medium as disclosed in Japanese Laid-Open Patent No. 1-113249, stripe-like unevenness (hereinafter, referred to as bond stripes) may occur in the recorded image at a boundary portion between recording scans, and the image quality may thus deteriorates.
Hereinafter, this problem will be described in detail.
FIGS. 1A to 1C are diagrams for describing the process of recording an image through a multipass recording method by using ink containing a resin emulsion and a recording medium having poor water absorbency. Here, a mode in which the image is completed through four instances of the recording scan will be described as an example.
FIG. 1A is a schematic diagram of an image surface obtained when the ink is ejected through the recording scan onto an area A of the recording medium. Dots 700 are formed in the area A upon the ink being ejected. Since the recording medium has poor water absorbency, the dots 700 are fixed so as to cover the surface of the recording medium.
FIG. 1B is a schematic diagram of the image surface obtained when the recording medium is conveyed in a Y direction after the recording scan illustrated in FIG. 1A and the ink is ejected onto an area B adjacent to the area A at a downstream side thereof in the Y direction. Here, films of the resin emulsion forming surface layers of the dots 700 are generally known to have high critical surface tension. The critical surface tension refers to a value unique to a solid surface, and indicates how wettable a liquid droplet is when the liquid droplet is applied onto the solid surface. It should be noted that a solid surface having high critical surface tension corresponds to a solid surface with which the applied liquid droplet is highly wettable. Therefore, if ink is ejected to a position that makes contact with the dot 700, the ink easily wets to spread over the dot 700 having high critical surface tension and is thus pulled in directions indicated by arrows in FIG. 1B. Meanwhile, dots 701 of the ink ejected to positions that do not make contact with the previously formed dots 700 are fixed without being pulled toward any particular direction.
FIG. 1C is a schematic diagram of an image surface obtained when the ink droplets ejected through the recording scan illustrated in FIG. 1B are fixed on the recording medium. As described above, force that pulls to a particular direction does not act on the dots 701 when the dots 701 are to be fixed, and thus the dots 701 are fixed at positions at which the ink droplets have been applied. Meanwhile, dots 702 are subjected to the force acting in the directions indicated by the arrows in FIG. 1B when the dots 702 are to be fixed, and thus the dots 702 are fixed at positions that are offset toward a side 1000 of the area A from the positions at which the ink droplets have been applied. As a result, a black stripe appears at the side 1000 of the area A and a white stripe appears at a side 1001 of the area B in a boundary portion between the area A and the area B on the recording medium, which corresponds to the boundary portion between the recording scans, and the image quality thus deteriorates.
It should be noted that the above problem occurs more notably when ink containing a resin emulsion is used.